Renocortical mRNA expression of vasoactive factors during spironolactone protective effect in chronic cyclosporine nephrotoxicity

Effect of Spironolactone on Kidney Function in Kidney Transplant Recipients (the SPIREN trial): A Randomized Placebo-Controlled Clinical Trial

Key Points

Spironolactone is safe for kidney transplant patients. Spironolactone reduces kidney function by an acute effect, whereafter it remains stable. Spironolactone does not affect the progression of interstitial fibrosis in protocol biopsies.

Background

Long-term kidney allograft survival is hampered by progressive interstitial fibrosis and tubular atrophy. The SPIREN trial tested the hypothesis that the mineralocorticoid receptor antagonist spironolactone stabilizes kidney function and attenuates glomerular barrier injury in kidney transplant patients treated with calcineurin inhibitors.

Methods

We conducted a randomized, placebo-controlled, double-blind clinical trial including 188 prevalent kidney transplant patients. Patients were randomized to spironolactone or placebo for 3 years. GFR was measured along with proteinuria and kidney fibrosis. The primary end point was change in measured GFR. Secondary outcomes were 24-hour proteinuria, kidney allograft fibrosis, and cardiovascular events. Measured GFRs, 24-hour proteinuria, and BP were determined yearly. Kidney biopsies were collected at baseline and after 2 years (n =48). Fibrosis was evaluated by quantitative stereology and classified according to Banff.

Results

The groups were comparable at baseline except for slightly older allografts in the spironolactone group. Spironolactone reduced measured GFRs (up to –7.6 [95% confidence interval, −10.9 to −4.3] ml/min compared with placebo) independently of time since transplantation and BP with no effect on the kidney function curve over time and reduced 24-hour proteinuria after 1 year. There was no significant effect of spironolactone on the development of interstitial fibrosis.

Conclusions

Spironolactone added to standard therapy for 3 years in kidney transplant patients did not improve kidney function, long-term proteinuria, or interstitial fibrosis.

Clinical Trial registration number

NCT01602861 .

Mineralocorticoid receptor antagonists in kidney transplantation

BACKGROUND

The fundamental role of the renin-angiotensin-aldosterone system in the pathophysiology of chronic kidney disease, congestive heart failure, hypertension and proteinuria is well established in pre-clinical and clinical studies. Mineralocorticoid receptor antagonists are among the primary options for renin-angiotensin-aldosterone system blockage, along with angiotensin-converting enzyme inhibitors and angiotensin receptor blockers.

METHODS

In this narrative review, we aim to evaluate the efficiency and safety of mineralocorticoid receptor antagonists in kidney transplant recipients, including the potential underlying pathophysiology.

RESULTS

The efficiency and safety of mineralocorticoid receptor antagonists in managing chronic kidney disease and proteinuria, either non-nephrotic or nephrotic range, have been demonstrated among nontransplanted patients, though studies investigating the role of mineralocorticoid receptor antagonists among kidney transplant recipients are scarce. Nevertheless, promising results have been reported in pre-clinical and clinical studies among kidney transplant recipients regarding the role of mineralocorticoid receptor antagonists in terms of ischaemia-reperfusion injury, proteinuria, or calcineurin inhibitor-mediated nephrotoxicity without considerable adverse events such as hypotension, hyperkalaemia or worsening renal functions.

CONCLUSION

Even though initial results regarding the role of mineralocorticoid receptor antagonist therapy for kidney transplant recipients are promising, there is clear need for large-scale randomized clinical trials with long-term follow-up data.

Long-term effect of eplerenone treatment in children with chronic allograft nephropathy

BACKGROUND

Literature supports the protective role of mineralocorticoid antagonist (MRA) against the renal injury induced by aldosterone in kidney transplant recipients. However, there is limited data available regarding the safety and efficacy of MRAs in pediatric renal transplant patients. Therefore, we aimed to investigate the effect of long-term eplerenone administration in children with chronic allograft nephropathy (CAN).

METHODS

Twenty-six renal transplant children with biopsy-proven CAN, an estimated glomerular filtration rate (eGFR ) > 40 mL/min per 1.73 m2 and with a significant proteinuria were included. Selected patients were randomly divided into two groups as follows; Group 1 (n = 10) patients received 25 mg/day eplerenone and Group 2 (n = 16) patients did not receive eplerenone for 36 months. Patients were examined in the renal transplant outpatient clinic biweekly for the first month and once a month thereafter. The primary outcome of the patients was compared.

RESULTS

Mean eGFR stayed stable in group 1 patients, but significantly decreased in group 2 at 36 months (57.53 ± 7.53 vs. 44.94 ± 8.04 mL/min per 1.73 m2 , p = .001). Similarly, spot protein-creatinine ratio was significantly lower in group 1 compared to group 2 patients at 36 months (1.02 ± 7.53 vs. 3.61 ± 0.53, p < .001). Eplerenone associated hyperkalemia was not observed in group 1 patients (4.6 ± 0.2 vs. 4.56 ± 0.3, p = .713).

CONCLUSION

The long-term eplerenone administration blunted the chronic allograft nephropathy by maintaining a stable eGFR levels and decreasing urine protein-creatinine ratio. Eplerenone associated hyperkalemia was not observed in our study.

The Mineralocorticoid Receptor on Smooth Muscle Cells Promotes Tacrolimus-Induced Renal Injury in Mice

Tacrolimus (Tac) is a calcineurin inhibitor commonly used as an immunosuppressor after solid organ transplantation. However, Tac may induce hypertension, nephrotoxicity, and an increase in aldosterone levels. The activation of the mineralocorticoid receptor (MR) is related to the proinflammatory status at the renal level. It modulates the vasoactive response as they are expressed on vascular smooth muscle cells (SMC). In this study, we investigated whether MR is involved in the renal damage generated by Tac and if the MR expressed in SMC is involved. Littermate control mice and mice with targeted deletion of the MR in SMC (SMC-MR-KO) were administered Tac (10 mg/Kg/d) for 10 days. Tac increased the blood pressure, plasma creatinine, expression of the renal induction of the interleukin (IL)-6 mRNA, and expression of neutrophil gelatinase-associated lipocalin (NGAL) protein, a marker of tubular damage (p < 0.05). Our study revealed that co-administration of spironolactone, an MR antagonist, or the absence of MR in SMC-MR-KO mice mitigated most of the unwanted effects of Tac. These results enhance our understanding of the involvement of MR in SMC during the adverse reactions of Tac treatment. Our findings provided an opportunity to design future studies considering the MR antagonism in transplanted subjects.

The mineralocorticoid receptor in chronic kidney disease

Chronic kidney disease (CKD) is a major public health concern, affecting approximately 10% of the population worldwide. CKD of glomerular or tubular origin leads to the activation of stress mechanisms, including the renin angiotensin aldosterone system and mineralocorticoid receptor (MR) activation. Over the last two decades, blockade of the MR has arisen as a potential therapeutic approach against various forms of kidney disease. In this review, we summarize the experimental studies that have shown a protective effect of MR antagonists (MRAs) in non-diabetic and diabetic CKD animal models. Moreover, we review the main clinical trials that have shown the clinical application of MRAs to reduce albuminuria and, importantly, to slow CKD progression. Recent evidence from the FIDELIO trial showed that the MRA finerenone can reduce hard kidney outcomes when added to the standard of care in CKD associated with type 2 diabetes. Finally, we discuss the effects of MRAs relative to those of SGLT2 inhibitors, as well as the potential benefit of combination therapy to maximize organ protection.

Oil-In-Water Microemulsion Encapsulation of Antagonist Drugs Prevents Renal Ischemia-Reperfusion Injury in Rats

Developing new therapeutic drugs to prevent ischemia/reperfusion (I/R)-induced renal injuries is highly pursued. Liposomal encapsulation of spironolactone (SP) as a mineralocorticoid antagonist increases dissolution rate, bioavailability and prevents the drug from degradation. In this context, this work develops a new formulation of oil-in-water type microemulsions to enhance the bioavailability of SP. The size of the SP-loaded microemulsion was about 6.0 nm by dynamic light scattering analysis. Briefly, we investigated the effects of nano-encapsulated SP (NESP) on renal oxidative stress, biochemical markers and histopathological changes in a rat model of renal I/R injury. Forty eight male Wistar rats were divided into six groups. Two groups served as control and injury model (I/R). Two groups received “conventional” SP administration (20 mg/kg) and NESP (20 mg/kg), respectively, for two days. The remaining two groups received SP (20 mg/kg) and NESP (20 mg/kg) two days before induction of I/R. At the end of the experiments, serum and kidneys of rats underwent biochemical, molecular and histological examinations. Our results showed that I/R induces renal oxidative stress, abnormal histological features and altered levels of renal biomarkers. Administration of SP in healthy animals did not cause any significant changes in the measured biochemical and histological parameters compared to the control group. However, SP administration in the I/R group caused some corrections in renal injury, although it could not completely restore I/R-induced renal oxidative stress and kidney damage. On the contrary, NESP administration restored kidney oxidative injury via decreasing renal lipid peroxidation and enhancing glutathione, superoxide dismutase and catalase in kidneys of the I/R group. The deviated serum levels of urea, creatinine, total proteins and uric acid were also normalized by NESP administration. Furthermore, NESP protected against renal abnormal histology features induced by I/R. Therefore, NESP has beneficial effects in preventing kidney damage and renal oxidative stress in a rat model of I/R, which deserves further evaluations in the future.

Effect of Fosfomycin on Cyclosporine Nephrotoxicity

Fosfomycin (Fos) has emerged as a potential treatment against multidrug-resistant organisms, however, there has been little work done on its influence on calcineurin inhibitor nephrotoxicity (CIN). This study was designed to evaluate the effect of Fos in combination with cyclosporine (CsA) on CIN. Two sets of experiments were undertaken. In the first, Wistar rats received different doses of Fos: 0, 62.5, 125, 250, and 500 mg/kg. In the second, rats were divided into four groups: control, CsA 15 mg/kg s.c., CsA + fosfomycin 62.5 mg/kg (CsA + LF), and CsA + Fos 500 mg/kg (CsA + HF). CsA was administrated daily for 14 days, whereas Fos administration started on the ninth day followed by two more doses, delivered 48 h apart. The administration of different Fos doses did not alter renal function. In contrast, CsA induced arteriolopathy, hypoperfusion, a reduction in the glomerular filtration rate, and downregulation of eNOS, angiotensinogen, and AT1R mRNA levels. Lower doses of Fos did not modify CIN. Instead, the CsA + HF group exhibited greater hypoperfusion, arteriolopathy, and oxidative stress, and increased mRNA levels of pro-inflammatory cytokines. This study shows that Fos administered by itself at different doses did not cause renal injury, but when it was given repeatedly at high dosages (500 mg/kg) in combination with CsA, it increased CIN through the promotion of greater oxidative stress and renal inflammation.

Aldosterone and the mineralocorticoid receptor in renal injury: A potential therapeutic target in feline chronic kidney disease

There is a growing body of experimental and clinical evidence supporting mineralocorticoid receptor (MR) activation as a powerful mediator of renal damage in laboratory animals and humans. Multiple pathophysiological mechanisms are proposed, with the strongest evidence supporting aldosterone-induced vasculopathy, exacerbation of oxidative stress and inflammation, and increased growth factor signalling promoting fibroblast proliferation and deranged extracellular matrix homeostasis. Further involvement of the MR is supported by extensive animal model experiments where MR antagonists (such as spironolactone and eplerenone) abrogate renal injury, including ischaemia-induced damage. Additionally, clinical trials have shown MR antagonists to be beneficial in human chronic kidney disease (CKD) in terms of reducing proteinuria and cardiovascular events, though current studies have not evaluated primary end points which allow conclusions to made about whether MR antagonists reduce mortality or slow CKD progression. Although differences between human and feline CKD exist, feline CKD shares many characteristics with human disease including tubulointerstitial fibrosis. This review evaluates the evidence for the role of the MR in renal injury and summarizes the literature concerning aldosterone in feline CKD. MR antagonists may represent a promising therapeutic strategy in feline CKD.

Vascular and inflammatory mineralocorticoid receptors in kidney disease

Mineralocorticoid receptor (MR) activation in the kidney can occur outside the aldosterone-sensitive distal nephron in sites including the endothelium, smooth muscle and inflammatory cells. MR activation in these cells has deleterious effects on kidney structure and function by promoting oxidative injury, endothelial dysfunction and stiffness, vascular remodelling and calcification, decreased relaxation and activation of T cells and pro-inflammatory macrophages. Here, we review the data showing the cellular consequences of MR activation in endothelial, smooth muscle and inflammatory cells and how this affects the kidney in pathological situations. The evidence demonstrating a benefit of pharmacological or genetic MR inhibition in various models of kidney disease is also discussed.

Resilience to acute kidney injury in offspring of maternal protein restriction

Protein restriction (PR) during pregnancy induces morphofunctional alterations related to deficient nephrogenesis. We studied the renal functional and morphological significance of PR during pregnancy and/or lactation in adult male rat offspring and the repercussions on acute kidney injury (AKI) severity. Female rats were randomly assigned to the following groups: control diet during pregnancy and lactation (CC), control diet during pregnancy and PR diet during lactation (CR), PR during pregnancy and control diet during lactation (RC), and PR during pregnancy and lactation (RR). Three months after birth, at least 12 male offspring of each group randomly underwent either bilateral renal ischemia for 45 min [ischemia-reperfusion (IR)] or sham surgery. Thus, eight groups were studied 24 h after reperfusion: CC, CC + IR, CR, CR + IR, RC, RC + IR, RR, and RR + IR. Under basal conditions, the CR, RC, and RR groups exhibited a significant reduction in nephron number that was associated with a reduction in renal blood flow. Glomerular hyperfiltration was present as a compensatory mechanism to maintain normal renal function. mRNA levels of several vasoactive, antioxidant, and anti-inflammatory molecules were decreased. After IR, renal function was similarly reduced in all of the studied groups. Although all of the offspring from maternal PR exhibited renal injury, the magnitude was lower in the RC and RR groups, which were associated with faster renal blood flow recovery, differential vasoactive factors, and hypoxia-inducible factor-1α signaling. Our results show that the offspring from maternal PR are resilient to AKI induced by IR that was associated with reduced tubular injury and a differential hemodynamic response.

Mineralocorticoid receptor antagonists and kidney diseases: pathophysiological basis

Chronic kidney disease (CKD) represents a global health concern, and its prevalence is increasing. The ultimate therapeutic option for CKD is kidney transplantation. However, the use of drugs that target specific pathways to delay or halt CKD progression, such as angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, and sodium-glucose co-transporter-2 (SGLT-2) inhibitors is limited in clinical practice. Mineralocorticoid receptor activation in nonclassical tissues, such as the endothelium, smooth muscle cells, inflammatory cells, podocytes, and fibroblasts may have deleterious effects on kidney structure and function. Several preclinical studies have shown that mineralocorticoid receptor antagonists (MRAs) ameliorate or cure kidney injury and dysfunction in different models of kidney disease. In this review, we present the preclinical evidence showing a benefit of MRAs in acute kidney injury, the transition from acute kidney injury to CKD, hypertensive and diabetic nephropathy, glomerulonephritis, and kidney toxicity induced by calcineurin inhibitors. We also discuss the molecular mechanisms responsible for renoprotection related to MRAs that lead to reduced oxidative stress, inflammation, fibrosis, and hemodynamic alterations. The available clinical data support a benefit of MRA in reducing proteinuria in diabetic kidney disease and improving cardiovascular outcomes in CKD patients. Moreover, a benefit of MRAs in kidney transplantation has also been observed. The past and present clinical trials describing the effect of MRAs on kidney injury are presented, and the risk of hyperkalemia and use of other options, such as potassium binding agents or nonsteroidal MRAs, are also addressed. Altogether, the available preclinical and clinical data support a benefit of using MRAs in CKD, an approach that should be further explored in future clinical trials.

Long-Term Effects of Spironolactone on Kidney Function and Hyperkalemia-Associated Hospitalization in Patients with Chronic Kidney Disease

Background: Spironolactone, a non-selective mineralocorticoid receptor antagonist, can protect against cardiac fibrosis and left ventricular dysfunction, and improve endothelial dysfunction and proteinuria. However, the safety and effects of spironolactone on patient-centered cardiovascular and renal endpoints remain unclear. Methods: We identified predialysis stage 3–4 chronic kidney disease (CKD) patients between 2000 and 2013 from the Longitudinal Health Insurance Database 2005 (LHID 2005). The outcomes of interest were end-stage renal disease (ESRD), major adverse cardiovascular events (MACE), hospitalization for heart failure (HHF), hyperkalemia-associated hospitalization (HKAH), all-cause mortality and cardiovascular mortality. The Fine and Gray sub-distribution hazards approach was adopted to adjust for the competing risk of death. Results: After the propensity score matching, 693 patients with stage 3–4 CKD were spironolactone users and 1386 were nonusers. During the follow-up period, spironolactone users had a lower incidence rate for ESRD than spironolactone non-users (39.2 vs. 53.69 per 1000 person-years) and a higher incidence rate for HKAH (54.79 vs. 18.57 per 1000 person-years). The adjusted hazard ratios for ESRD of spironolactone users versus non-users were 0.66 (95% CI, 0.51–0.84; p value < 0.001) and 3.17 (95% CI, 2.41–4.17; p value < 0.001) for HKAH. A dose-response relationship was found between spironolactone use and risk of ESRD and HKAH. There were no statistical differences in MACE, HHF, all-cause mortality and cardiovascular mortality between spironolactone users and non-users. Conclusion: Spironolactone represented a promising treatment option to retard CKD progression to ESRD amongst stage 3–4 CKD patients, but strategic treatments to prevent hyperkalemia should be enforced.

The effect of spironolactone on calcineurin inhibitor induced nephrotoxicity: a multicenter randomized, double-blind, clinical trial (the SPIREN trial)

Background

Calcineurin inhibitor induced nephrotoxicity contributes to late allograft failure in kidney transplant patients. Evidence points towards aldosterone to play a role in the development of fibrosis in multiple organs. Animal studies have indicated a beneficial effect of mineralocorticoid receptor antagonists preventing calcineurin inhibitor induced nephrotoxicity. Only few studies have explored this effect in humans. The objective of this study is to evaluate the effect of spironolactone on glomerular filtration rate and fibrosis in kidney transplant patients.

Method

Prospective, double-blind, randomized, clinical trial including 170 prevalent kidney transplant patients. Patients are randomized to spironolactone 25–50 mg/day or placebo for three years. Primary outcome is glomerular filtration rate evaluated by chrome-EDTA clearance. Secondary outcomes are 24-h protein excretion, amount of interstitial fibrosis in renal allograft biopsies, and cardiovascular events. As an exploratory outcome, we aim to identify markers of fibrosis in blood and urine.

Discussion

Long term allograft survival remains a key issue in renal transplantation, partly due to calcineurin inhibitor induced nephrotoxicity. Evidence from animal- and small human studies indicate a beneficial effect of mineralocorticoid receptor antagonism on renal function and fibrosis. This study aims to test this hypothesis in a sufficiently powered randomized clinical trial. Results might influence the future management of long term allograft survival in renal transplantation.

Trial registration

ClinicalTrials.gov identifier (05/17/2012): NCT01602861. EudraCT number (05/31/2011): 2011–002243-98.

Cyclosporine A induces endothelin-converting enzyme-1: Studies in vivo and in vitro

AIM

Cyclosporine A (CsA) induces renal vasoconstriction and hypoxia and enhances the expression of endothelin-1 (ET-1) pro-hormone (pre-pro-ET-1), plausibly leading to a feed-forward loop of renal vasoconstriction, hypoxia and enhanced synthesis of the potent vasoconstrictor ET-1. Endothelin-converting enzyme (ECE)-1 cleaves big endothelin to generate endothelin (ET)-1 and is upregulated by hypoxia via hypoxia-inducible factor (HIF). We hypothesized that in addition to the direct induction of ET-1 synthesis, CsA might also intensify renal ECE-1 expression, thus contributing to enhanced ET-1 synthesis following CsA.

METHODS

CsA was administered to Sprague Dawley rats (120 mg/kg/SC) for 4 days, and renal HIF and ECE-1 expression were assessed with Western blots and immunostaining. Human umbilical vein endothelial cells (HUVEC) and proximal tubular cell line (HK-2) were subjected to CsA, and ECE-1 induction was evaluated using real-time mRNA PCR and Western blots.

RESULTS

Cyclosporine A intensified renal parenchymal ECE-1 expression in the rat kidney, particularly in distal nephron segments, along with renal hypoxia (detected by pimonidazole adducts) and HIF expression, in line with our recent observations showing episodic hypoxia in mice subjected to CsA. Furthermore, in cultured normoxic HUVEC and HK-2 cells, CsA dose-dependently induced both pre-pro-ET-1 and ECE-1 mRNA and protein expression, with enhanced ET-1 generation.

CONCLUSION

CsA induces ECE-1 via both hypoxic and non-hypoxic pathways. ECE-1 may contribute to increased renal ET-1 generation following CsA, participating in a feed-forward loop of renal parenchymal hypoxia and ET synthesis.

Does Mineralocorticoid Receptor Antagonism Prevent Calcineurin Inhibitor-Induced Nephrotoxicity?

Calcineurin inhibitors have markedly reduced acute rejection rates in renal transplantation, thus significantly improved short-term outcome. The beneficial effects are, however, tampered by acute and chronic nephrotoxicity leading to interstitial fibrosis and tubular atrophy, which impairs long-term allograft survival. The mineralocorticoid hormone aldosterone induces fibrosis in numerous organs, including the kidney. Evidence from animal models suggests a beneficial effect of aldosterone antagonism in reducing calcineurin inhibitor-induced nephrotoxicity. This review summarizes current evidence of mineralocorticoid receptor antagonism in animal models of calcineurin inhibitor-induced nephrotoxicity and the results from studies of mineralocorticoid antagonism in renal transplant patients.

Randomized Controlled Trial of Mineralocorticoid Receptor Blockade in Children with Chronic Kidney Allograft Nephropathy

BACKGROUND AND OBJECTIVES

We showed that mineralocorticoid receptor blockade (MRB) prevented acute and chronic cyclosporine nephropathy (CsA-Nx) in the rat. The aim of this translational study was to investigate the effect of long-term eplerenone administration on renal allograft function in children with biopsy-proven chronic allograft nephropathy (CAN).

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Renal transplant children <18 years, biopsy-proven CAN, and a GFR>40 ml/min per 1.73 m2 were included. Patients with BK virus active nephritis, recurrence of renal disease, GFR decline in previous 3 months, or treated with calcium antagonists or antifungal drugs were excluded. They were randomized to receive placebo (n=10) or eplerenone 25 mg/d for 24 months (n=13). Visits were scheduled at baseline, 6, 12, and 24 months. At each period, a complete clinical examination was performed and blood and urine samples were taken. Urine creatinine, 8-hydroxylated-guanosine, heat shock protein 72 (HSP72), and kidney injury molecule (KIM-1) levels were also assessed. In kidney biopsy samples, the tubulo-interstitial area affected by fibrosis (TIF) and glomerulosclerosis were measured at baseline and after 24 months.

RESULTS

The baseline eGFR was 80±6 in the placebo and 86±6 ml/min per 1.73 m2 in the eplerenone group; at 24 months it was 66±8 and 81±7 ml/min per 1.73 m2, respectively (P=0.33; 95% confidence intervals, -18 to 33 at baseline, and -11 to 40 after 24 months). The albumin-to-creatinine ratio was 110±74 in the placebo, and 265±140 mg/g in the eplerenone group; and after 24 months it was 276±140 and 228±88 mg/g, respectively (P=0.15; 95% confidence intervals, -283 to 593, and -485 to 391, respectively). In addition, the placebo exhibited a greater TIF, glomerulosclerosis, and urinary HSP72 compared with the eplerenone group.

CONCLUSIONS

Although this study was underpowered to provide definitive evidence that long-term eplerenone administration attenuates the progression of CAN in pediatric transplant patients, it encourages testing the potential benefit of MRB in this pediatric population.

Nonsteroidal Mineralocorticoid Receptor Antagonist Finerenone Protects Against Acute Kidney Injury-Mediated Chronic Kidney Disease: Role of Oxidative Stress

Acute kidney injury induced by ischemia/reperfusion (IR) is a frequent complication in hospitalized patients. Mineralocorticoid receptor antagonism has shown to be helpful against renal IR consequences; however, the potential benefit of novel nonsteroidal mineralocorticoid receptor antagonists such as finerenone has to be further explored. In this study, we evaluated the efficacy of finerenone to prevent the acute and chronic consequences of ischemic acute kidney injury. For the acute study (24 hours), 18 rats were divided into sham, bilateral renal ischemia of 25 minutes, and rats that received 3 doses of finerenone at 48, 24, and 1 hour before the ischemia. For the chronic study (4 months), 23 rats were divided into sham, rats that underwent 45 minutes of bilateral ischemia, and rats treated with finerenone at days 2 and 1 and 1 hour before IR. We found that after 24 hours of reperfusion, the untreated IR rats presented kidney dysfunction and tubular injury. Kidney injury molecule-1 and neutrophil gelatinase associated to lipolacin mRNA levels were increased. In contrast, the rats treated with finerenone displayed normal kidney function and significantly lesser tubular injury and kidney injury molecule-1 and neutrophil gelatinase associated to lipolacin levels. After 4 months, the IR rats developed chronic kidney disease, evidenced by kidney dysfunction, increased proteinuria and renal vascular resistance, tubular dilation, extensive tubule-interstitial fibrosis, and an increase in kidney transforming growth factor-β and collagen-I mRNA. The transition from acute kidney injury to chronic kidney disease was fully prevented by finerenone. Altogether, our data show that in the rat, finerenone is able to prevent acute kidney injury induced by IR and the chronic and progressive deterioration of kidney function and structure.

Deletion of mineralocorticoid receptors in smooth muscle cells blunts renal vascular resistance following acute cyclosporine administration

Calcineurin inhibitors such as cyclosporine A (CsA) are still commonly used after renal transplantation, despite CsA--induced nephrotoxicity (CIN), which is partly related to vasoactive mechanisms. The mineralocorticoid receptor (MR) is now recognized as a key player in the control of vascular tone, and both endothelial cell- and vascular smooth muscle cell (SMC)-MR modulate the vasoactive responses to vasodilators and vasoconstrictors. Here we tested whether vascular MR is involved in renal hemodynamic changes induced by CsA. The relative contribution of vascular MR in acute CsA treatment was evaluated using mouse models with targeted deletion of MR in endothelial cell or SMC. Results indicate that MR expressed in SMC, but not in endothelium, contributes to the increase of plasma urea and creatinine, the appearance of isometric tubular vacuolization, and overexpression of a kidney injury biomarker (neutrophil gelatinase--associated lipocalin) after CsA treatment. Inactivation of MR in SMC blunted CsA--induced phosphorylation of contractile proteins. Finally, the in vivo increase of renal vascular resistance induced by CsA was blunted when MR was deleted from SMC cells, and this was associated with decreased L-type Ca2D channel activity. Thus, our study provides new insights into the role of vascular MR in renal hemodynamics during acute CIN, and provides rationale for clinical studies of MR antagonism to manage the side effects of calcineurin inhibitors.

Safety of Eplerenone for Kidney-Transplant Recipients with Impaired Renal Function and Receiving Cyclosporine A

Background

Animal studies have highlighted the role of vascular mineralocorticoid receptor during Cyclosporine A-induced nephrotoxicity. Mineralocorticoid receptor antagonists could improve kidney survival but are not commonly used during renal impairment and in association with several immunosuppressive drugs due to a supposed higher risk of adverse events. We tested the tolerance of eplerenone according to its expected adverse events: hyperkalemia, metabolic acidosis, hypotension, acute kidney failure, or any other adverse event.

Methods

We conducted a single-center, prospective, open-label study in 31 kidney-transplant recipients with impaired renal function (30 and 50 mL/min/1.73m²) and receiving cyclosporine A. All patients received eplerenone 25 mg/d for 8 weeks. Serum potassium, renal function and expected adverse events were closely monitored.

Results

Eight patients experienced mild hyperkalemia (>5 mmol/L), one moderate hyperkalemia (>5.5 mmol/L) and had to receive potassium-exchange resin. No severe hyperkalemia (>6 mmol/L) occurred. One acute kidney failure was observed, secondary to diarrhea. Basal serum potassium and bicarbonate were independently associated with a higher risk of developing mild hyperkalemia (>5 mmol/L) under treatment (OR 6.5, p = 0.003 and 0.7, p = 0.007, respectively). A cut-off value of 4.35 mmol/L for basal serum potassium was the best factor to predict the risk of developing mild hyperkalemia (>5 mmol/L).

Conclusions

Until eGFR falls to 30 mL/min/1.73m², eplerenone could be safely given to kidney-transplant recipients receiving cyclosporine A, if kalemia is closely monitored. When renal function is impaired and if basal kalemia is >4.35 mmol/L, then clinicians should properly balance risk and benefit of eplerenone use and offer dietary advice. An adequately powered prospective randomized study is now needed to test its efficiency (and safety) in this population.

Trial Registration

ClinicalTrials.gov NCT01834768

The effects of A2B receptor modulators on vascular endothelial growth factor and nitric oxide axis in chronic cyclosporine nephropathy

Introduction:

To investigate the actions of adenosine A_2B receptor modulators on VEGF and NO levels in CsA nephropathy.

Materials and Methods:

Nephropathy was induced by administrating 25 mg/kg (s.c) of CsA for 5 weeks. The VEGF and NO levels were measured in kidney tissue. Serum creatinine, creatinine clearance, urinary albumin excretion, blood urea nitrogen, kidney pathology score were measured to assess renal function. The analysis of mRNA expression of A_2B receptor and VEGF was performed.

Results:

Administration of CsA for 5 weeks induced adverse renal function. The mRNA expression of VEGF was reduced in renal tissue after 5 weeks of CsA treatment. The renal VEGF and NO levels were also reduced in these animals. In vivo administration of A_2B adenosine receptor agonist increased renal VEGF which was inhibited by a selective A_2B AR antagonist (MRS1754) in CsA-treated animals. The increase in VEGF was associated with reversal of adverse renal functions. The effects of A_2B AR modulators were prominent in CsA-treated animals compared with control animals suggesting CsA treatment may upregulate A_2B ARs. The mRNA expression of A_2B AR was increased after 5 weeks of CsA.

Conclusions:

A_2B AR modulators may provide new therapeutic options to retard CsA nephropathy by mediating renal VEGF and NO.

Aldosterone blockade in chronic kidney disease

Although blockade of the renin-angiotensin-aldosterone system with angiotensin-converting enzyme inhibitors or angiotensin-receptor blockers has become standard therapy for chronic kidney disease (CKD), renewed interest in the role of aldosterone in mediating the injuries and progressive insults of CKD has highlighted the potential role of treatments targeting the mineralocorticoid receptor (MR). Although salt restriction is an important component of mitigating the profibrotic effects of MR activation, a growing body of literature has shown that MR antagonists, spironolactone and eplerenone, can reduce proteinuria and blood pressure in patients at all stages of CKD. These agents carry a risk of hyperkalemia, but this risk likely can be predicted based on baseline renal function and mitigated using dietary modifications and adjustments of concomitant medications. Data on hard outcomes, such as progression to end-stage renal disease and overall mortality, still are lacking in patients with CKD.

Celecoxib offsets the negative renal influences of cyclosporine via modulation of the TGF-β1/IL-2/COX-2/endothelin ET(B) receptor cascade

Endothelin (ET) signaling provokes nephrotoxicity induced by the immunosuppressant drug cyclosporine A (CSA). We tested the hypotheses that (i): celecoxib, a selective cyclooxygenase-2 (COX-2) inhibitor, counterbalances renal derangements caused by CSA in rats and (ii) the COX-2/endothelin ET(B) receptor signaling mediates the CSA-celecoxib interaction. Ten-day treatment with CSA (20 mg/kg/day) significantly increased biochemical indices of renal function (serum urea, creatinine), inflammation (interleukin-2, IL-2) and fibrosis (transforming growth factor-β₁, TGF-β₁). Histologically, CSA caused renal tubular atrophy along with interstitial fibrosis. These detrimental renal effects of CSA were largely reduced in rats treated concurrently with celecoxib (10 mg/kg/day). We also report that cortical glomerular and medullary tubular protein expressions of COX-2 and ET(B) receptors were reduced by CSA and restored to near-control values in rats treated simultaneously with celecoxib. The importance of ET(B) receptors in renal control and in the CSA-celecoxib interaction was further verified by the findings (i) most of the adverse biochemical, inflammatory, and histopathological profiles of CSA were replicated in rats treated with the endothelin ETB receptor antagonist BQ788 (0.1 mg/kg/day, 10 days), and (ii) the BQ788 effects, like those of CSA, were alleviated in rats treated concurrently with celecoxib. Together, the data suggest that the facilitation of the interplay between the TGF-β1/IL-2/COX-2 pathway and the endothelin ET(B) receptors constitutes the cellular mechanism by which celecoxib ameliorates the nephrotoxic manifestations of CSA in rats.

Mineralocorticoid receptor blockade reduced oxidative stress in renal transplant recipients: a double-blind, randomized pilot study

BACKGROUND

Previous experimental studies from our laboratory have demonstrated that aldosterone plays a central role in renal ischemic processes. This study was designed to evaluate the effect of mineralocorticoid receptor blockade in renal transplant recipients from living donors.

METHODS

20 adult kidney transplant recipients from living donors were included in a double-blind, randomized, placebo-controlled clinical pilot study that compared spironolactone and placebo. Placebo or spironolactone (25 mg) was administered 1 day before and 3 days posttransplantation. Renal function and urinary kidney injury molecule-1, interleukin-18, and heat shock protein 72 as well as urinary hydrogen peroxide (H2O2) levels were quantified.

RESULTS

No significant differences were seen between the groups studied regarding age, gender, indication for kidney transplantation, residual renal function, renal replacement therapy, or warm and cold ischemia periods. In contrast, spironolactone administration significantly reduced the oxidative stress assessed by the urinary H2O2 excretion, in spite of no differences in renal function or reduction in tubular injury biomarkers.

CONCLUSIONS

The findings of this exploratory study strongly suggest that aldosterone promotes oxidative stress and that the administration of spironolactone reduces the production of urinary H2O2 as a result of lesser formation of surrogate reactive oxygen species secondary to the ischemia-reperfusion phenomenon.

The mineralocorticoid receptor antagonist eplerenone reduces renal interstitial fibrosis after long-term cyclosporine treatment in rat: antagonizing cyclosporine nephrotoxicity

Background

Chronic cyclosporine-(CsA)-mediated loss of kidney function is a major clinical problem in organ transplantation. We hypothesized that the mineralocorticoid receptor antagonist eplerenone (EPL) prevents chronic CsA-induced renal interstitial volume increase, tubule loss, and functional impairment in a rat model.

Methods

Sprague–Dawley rats received CsA alone (15 mg/kg/d p.o.), CsA and EPL (approximately 100 mg/kg/day p.o.) or vehicle (control) for 12 weeks. At 11 weeks, chronic indwelling arterial and venous catheters were implanted for continuous measurements of arterial blood pressure (BP) and GFR (inulin clearance) in conscious, freely moving animals. Plasma was sampled for analysis and kidney tissue was fixed for quantitative stereological analyses.

Results

Compared to controls, CsA-treatment reduced relative tubular volume (0.73±0.03 vs. 0.85±0.01, p<0.05) and increased relative interstitial volume (0.080±0.004 vs. 0.045±0.003, p<0.05); EPL attenuated these changes (0.82±0.02, p<0.05, and 0.060±0.006, p<0.05, respectively). CsA-treated rats had more sclerotic glomeruli and a higher degree of vascular depositions in arterioles; both were significantly reduced in CsA+EPL-treated animals. CsA increased BP and reduced body weight gain and GFR. In CsA+EPL rats, weight gain, GFR and BP at rest (daytime) were normalized; however, BP during activity (night) remained elevated. Plasma sodium and potassium concentrations, kidney-to-body weight ratios and CsA whole blood concentration were similar in CsA and CsA+EPL rats.

Conclusions

It is concluded that in the chronic cyclosporine rat nephropathy model, EPL reduces renal tissue injury, hypofiltration, hypertension, and growth impairment. MR antagonists should be tested for their renoprotective potential in patients treated with calcineurin inhibitors.

Spironolactone prevents chronic kidney disease caused by ischemic acute kidney injury

Acute kidney injury (AKI) has been recognized as a risk factor for the development of chronic kidney disease (CKD). Aldosterone has a critical role in promoting renal injury induced by ischemia. Here, we evaluated whether spironolactone administered before or after AKI caused by ischemia protects against CKD. In the first set of experiments, Wistar rats underwent a sham operation without or with prior spironolactone treatment, or underwent 45 minutes of bilateral renal ischemia without or with spironolactone treatment before ischemia and assessed over 270 days. The second set of rats received low (20 mg/kg) or high (80 mg/kg) doses of spironolactone at three different times after the sham operation or bilateral renal ischemia and were assessed after 90 days. Untreated animals developed CKD following ischemia-induced AKI as characterized by a progressive increase in proteinuria, renal dysfunction, podocyte injury, glomerular hypertrophy, and focal sclerosis. This was associated with increased oxidative stress, an upregulation of tumor growth factor (TGF)-β, followed by upregulation of the TGF-β downstream effectors phospho-Smad3, collagen I, fibronectin, and proinflammatory cytokines. Treatment with spironolactone either before or after ischemia prevented subsequent CKD by avoiding the activation of fibrotic and inflammatory pathways. Thus, spironolactone may be a promising treatment for the prevention of AKI-induced CKD.

[Aldosterone and kidney diseases: an emergent paradigm with important clinical implications]

Slowing the progression of chronic kidney diseases needs new efficient treatments. Aldosterone classically acts on the distal nephron: it allows sodium reabsorption, potassium secretion and participates to blood volume control. Recently, new targets of aldosterone have been described including the heart and the vasculature but also non-epithelial kidney cells such as mesangial cells, podocytes and renal fibroblasts. The pathophysiological implication of aldosterone and its receptor, the mineralocorticoid receptor has been demonstrated ex vivo in cell culture and in vivo in experimental animal models with kidney damages such as diabetic and hypertensive kidney nephropathies, chronic kidney disease and glomerulopathies. The beneficial effects of the pharmacological antagonists of the mineralocorticoid receptor are independent of the hypertensive effect of aldosterone, indicating that blocking the activation of the mineralocorticoid receptor in these non-classical renal targets may be of clinical importance. Several clinical studies now report benefit and safety when using spironolactone or eplerenone, the currently available mineralocorticoid receptor antagonists, in patients with kidney diseases. In this review, we discuss the recent results reported in experimental and clinical research in this domain.

RGS4 controls renal blood flow and inhibits cyclosporine-mediated nephrotoxicity

Calcineurin inhibitors (CNI) are powerful immunomodulatory agents that produce marked renal dysfunction due in part to endothelin-1-mediated reductions in renal blood flow. Ligand-stimulated Gq protein signaling promotes the contraction of smooth muscle cells via phospholipase Cbeta-mediated stimulation of cytosolic calcium release. RGS4 is a GTPase activating protein that promotes the deactivation of Gq and Gi family members. To investigate the role of G protein-mediated signaling in the pathogenesis of CNI-mediated renal injury, we used mice deficient for RGS4 (rgs4(-/-)). Compared to congenic wild type control animals, rgs4(-/-) mice were intolerant of the CNI, cyclosporine (CyA), rapidly developing fatal renal failure. Rgs4(-/-) mice exhibited markedly reduced renal blood flow after CyA treatment when compared to congenic wild type control mice as measured by magnetic resonance imaging (MRI). Hypoperfusion was reversed by coadministration of CyA with the endothelin antagonist, bosentan. The MAPK/ERK pathway was activated by cyclosporine administration and was inhibited by cotreatment with bosentan. These results show that endothelin-1-mediated Gq protein signaling plays a key role in the pathogenesis of vasoconstrictive renal injury and that RGS4 antagonizes the deleterious effects of excess endothelin receptor activation in the kidney.

Adrenalectomy prevents renal ischemia-reperfusion injury

Spironolactone treatment prevents renal damage induced by ischemia-reperfusion (I/R), suggesting that renoprotection conferred by spironolactone is mediated by mineralocorticoid receptor (MR) blockade. It is possible, however, that this effect is due to other mechanisms. Therefore, this study evaluated whether adrenalectomy prevented renal damage induced by I/R. Three groups of Wistar rats were studied: 1) a group subjected to a sham surgery, 2) a group subjected to bilateral I/R, and 3) a group of rats in which adrenal glands were removed 3 days before induction of I/R. As expected, I/R resulted in renal dysfunction and severe tubular injury that was associated with a significant increase in tubular damage markers. In contrast, there was no renal dysfunction or tubular injury in rats that were adrenalectomized before I/R. These effects were demonstrated by normalization of glomerular filtration rate, markers of oxidative stress, and tubular injury markers in adrenalectomized rats. The renoprotection observed was associated with the reestablishment of nitric oxide metabolites, increased endothelial nitric oxide synthase expression and its activating phosphorylation, as well as normalization of Rho-kinase expression and ETA mRNA levels. Our results show that aldosterone plays a central role in the pathogenesis of renal damage induced by I/R and that MR blockade may be a promising strategy that opens a new therapeutic option for preventing acute renal injury.

Calcineurin inhibitor nephrotoxicity

The use of the calcineurin inhibitors cyclosporine and tacrolimus led to major advances in the field of transplantation, with excellent short-term outcome. However, the chronic nephrotoxicity of these drugs is the Achilles' heel of current immunosuppressive regimens. In this review, the authors summarize the clinical features and histologic appearance of both acute and chronic calcineurin inhibitor nephrotoxicity in renal and nonrenal transplantation, together with the pitfalls in its diagnosis. The authors also review the available literature on the physiologic and molecular mechanisms underlying acute and chronic calcineurin inhibitor nephrotoxicity, and demonstrate that its development is related to both reversible alterations and irreversible damage to all compartments of the kidneys, including glomeruli, arterioles, and tubulo-interstitium. The main question--whether nephrotoxicity is secondary to the actions of cyclosporine and tacrolimus on the calcineurin-NFAT pathway--remains largely unanswered. The authors critically review the current evidence relating systemic blood levels of cyclosporine and tacrolimus to calcineurin inhibitor nephrotoxicity, and summarize the data suggesting that local exposure to cyclosporine or tacrolimus could be more important than systemic exposure. Finally, other local susceptibility factors for calcineurin inhibitor nephrotoxicity are reviewed, including variability in P-glycoprotein and CYP3A4/5 expression or activity, older kidney age, salt depletion, the use of nonsteroidal anti-inflammatory drugs, and genetic polymorphisms in genes like TGF-beta and ACE. Better insight into the mechanisms underlying calcineurin inhibitor nephrotoxicity might pave the way toward more targeted therapy or prevention of calcineurin inhibitor nephrotoxicity.

Established and newly proposed mechanisms of chronic cyclosporine nephropathy

Cyclosporine (CsA) has improved patient and graft survival rates following solid-organ transplantation and has shown significant clinical benefits in the management of autoimmune diseases. However, the clinical use of CsA is often limited by acute or chronic nephropathy, which remains a major problem. Acute nephropathy depends on the dosage of CsA and appears to be caused by a reduction in renal blood flow related to afferent arteriolar vasoconstriction. However, the mechanisms underlying chronic CsA nephropathy are not completely understood. Activation of the intrarenal renin-angiotensin system (RAS), increased release of endothelin-1, dysregulation of nitric oxide (NO) and NO synthase, up-regulation of transforming growth factor-beta1 (TGF-beta1), inappropriate apoptosis, stimulation of inflammatory mediators, enhanced innate immunity, endoplasmic reticulum stress, and autophagy have all been implicated in the pathogenesis of chronic CsA nephropathy. Reducing the CsA dosage or using other renoprotective drugs (angiotensin II receptor antagonist, mycophenolate mofetil, and statins, etc.) may ameliorate chronic CsA-induced renal injury. This review discusses old and new concepts in CsA nephropathy and preventive strategies for this clinical dilemma.

The effect of aldosterone antagonist in experimental nephropathy induced by cyclosporine A

This study evaluated the effect of spironolactone in the renal function alterations induced by cyclosporine A (CsA) in rats.

METHODS

Male Wistar rats fed with an unrestricted sodium diet received CsA 15 mg/kg/day or CsA at the same dosage plus 20 mg/kg/day of spironolactone. Another group received only saline. The animals that had proteinuria > 50 mg/24h or serum creatinine > 1.0 mg% were excluded, and after five weeks, the remaining rats were analyzed again for these parameters. At the end of the fifth week, these animals were also sacrificed, and their kidneys were analyzed histologically.

RESULTS

The animals that received CsA isolated or in association with spironolactone presented increase in serum creatinine. However, the comparison of the relative variation [Delta% = ([final - initial] / initial) x 100] of the serum creatinine concentrations in the beginning and at the end of the experiment among the animal groups showed a significant increase in the CsA group compared with the saline group (44.17 +/- 30.7% vs. -6.19 +/- 14.5%; p = 0.005), whereas there was no difference between the CsA + spironolactone and the saline group. In all of the animal groups, the values of 24-hour proteinuria were similar at the end of the experiment, and no renal histological alterations were observed.

CONCLUSION

This experimental model of nephrotoxicity by CsA in rats without salt restriction in the diet showed that CsA reduced the glomerular filtration and suggested that the blockage of aldosterone receptors prevented, at least partially, the reduction in renal function induced by CsA.

Renal ischemia-reperfusion injury is prevented by the mineralocorticoid receptor blocker spironolactone

Renal ischemia and reperfusion (I/R) injury is the major cause of acute renal failure and may also be involved in the development and progression of some forms of chronic kidney disease. We previously showed that a mineralocorticoid receptor (MR) blockade prevents renal vasoconstriction induced by cyclosporine that leads to acute and chronic renal failure (Feria I, Pichardo I, Juarez P, Ramirez V, Gonzalez MA, Uribe N, Garcia-Torres R, Lopez-Casillas F, Gamba G, Bobadilla NA. Kidney Int 63: 43–52, 2003; Perez-Rojas JM, Derive S, Blanco JA, Cruz C, Martinez de la Maza L, Gamba G, Bobadilla NA. Am J Physiol Renal Physiol 289: F1020–F1030, 2005). Thus we investigated whether spironolactone administration prevents the functional and structural damage induced by renal ischemia-reperfusion (I/R). Five groups were studied: sham-operated animals, rats that underwent 20 min of ischemia and 24 h of reperfusion, and three groups that received spironolactone 1, 2, or 3 days before I/R, respectively. Renal I/R produced significant renal dysfunction and tubular damage. Spironolactone administration completely prevented a decrease in renal blood flow, the development of acute renal failure, and tubular apoptosis. The protection conferred by spironolactone was characterized by decreasing oxidative stress, as evidenced by a reduction in kidney lipoperoxidation, increasing expression of antioxidant enzymes, and restoration of urinary NO2/NO3 excretion. Endothelial nitric oxide synthase expression was upregulated by a mineralocorticoid receptor blockade in I/R groups; in addition, an increase in activating phosphorylation of this enzyme at residue S1177 and a decrease in inactivating phosphorylation at T497 were observed. In conclusion, our study shows that spironolactone administration prevents the renal injury induced by I/R, suggesting that aldosterone plays a central role in this model of renal injury.

New insights into the pathophysiology of cyclosporine nephrotoxicity: a role of aldosterone

Cyclosporine A (CsA), a calcineurin inhibitor, has improved allograft survival in solid organ transplantation and has been increasingly applied in the management of autoimmune diseases. While marked progress has been made in patient and allograft survival rates, clinical use of CsA is often limited by its nephrotoxic effect, which can be presented as two distinct and well-characterized forms: acute and chronic nephrotoxicity. The acute form is characterized by renal vasoconstriction, induced by an imbalance of vasoactive substances release, which leads to renal dysfunction. This form is reversible. The chronic toxicity, in contrast, is characterized by the vasoconstriction plus the development of structural damage that includes arteriolopathy and tubulointerstitial fibrosis that are often not reversible. The exact mechanisms of these deleterious effects are not fully understood, but major advances have occurred over the last few years. Here we review the current literature regarding the pathogenesis and strategies that have been used to ameliorate renal injury in chronic CsA nephrotoxicity. Recent observations suggest that aldosterone plays a central role in the pathogenesis of CsA nephrotoxicity and that spironolactone could be a useful agent to prevent it. These studies and the use of mineralocorticoid receptor blockade are discussed.

Mineralocorticoid receptor blockade confers renoprotection in preexisting chronic cyclosporine nephrotoxicity

Recent studies from our laboratory have shown that the mineralocorticoid receptor (MR) blockade with spironolactone (Sp) prevented renal dysfunction and reduced renal injury in both acute and chronic cyclosporine (CsA) nephrotoxicity. This study was designed to evaluate whether Sp administration reduces functional and structural renal damage associated in the setting of preexisting chronic CsA nephrotoxicity. Twenty eight male Wistar rats were fed a low-sodium diet. Fourteen received vehicle (V) and the others were treated with CsA (15 mg/kg sc). After 18 days one half of each group received Sp (20 mg/kg po) for the subsequent 18 days. Creatinine clearance, arteriolopathy, tubulointerstitial fibrosis, arteriolar thickening, glomerular diameter, apoptosis index and TGF-beta, procaspase-3, and kidney injury molecule 1 (Kim-1) mRNA levels as well as Kim-1 shedding in urine were evaluated. Sp reduced the progression of renal dysfunction and tubulointerstitial fibrosis in preexisting chronic CsA nephrotoxicity. There was a significant reduction of arteriolar thickening in the CsA+Sp group that was associated with greater glomerular diameter and reduction of apoptosis index. These renoprotective effects were associated with reduction of TGF-beta, procaspase-3, and Kim-1 mRNA levels as well as Kim-1 shedding into the urine. In conclusion, MR blockade with Sp prevented the progression of renal injury in preexisting chronic CsA nephropathy. These results suggest that Sp may reduce CsA-induced established nephrotoxicity in patients.